Conventional inversion recovery (IR) methods in magnetic resonance imaging (MRI) can be used to suppress a signal from a specific tissue and, as such, leverage the image contrast in adjacent tissues. For example late enhancement IR imaging may be used to diagnose a wide range of ischemic and non-ischemic cardiomyopathies. In this application, a gadolinium-based extracellular contrast agent (e.g., gadolinium-DTPA) which is administered intravenously to shorten the T1 relaxation time of protons in the tissue of interest. The gadolinium remains in infarcted tissue long after it washes out of the surrounding normal myocardium and, by obtaining images multiple minutes after the injection, a high image contrast can be obtained between the healthy myocardium and the fibrosis. This is referred to as late gadolinium enhanced (LGE) imaging. The resulting contrast can be best appreciated using IR imaging to null the signal of the healthy myocardium.
The TI time for optimal myocardial nulling (TInull) depends on a number of factors, including IR imaging pulse sequence used, patient age, cardiac function, magnetic field strength, a volume of the contrast bolus, and a time between a contrast injection and a scan. This optimal TI time is typically estimated using a TI scout sequence. This sequence acquires a segmented cine series of images covering a range of time points following an inversion pulse, wherein each segment corresponds to a different TI. An MRI operator visually selects a TI time where the signal intensity in the healthy myocardium is minimal and subsequently runs a higher resolution IR scan using this optimal TI time. An offset in TI is typically added to compensate for the sequence differences between the TI scout and the IR scan. In conventional systems, T1 and the optimal TI are estimated using a segmented cine inversion recovery sequence, but these systems are difficult to automate as they are based on a series of images which differ both in contrast and cardiac phase.